Yes, the line between general ship types and specialized ship types is a bit fuzzy. I did the best I could.
The British Interplanetary Society (BIS) in general, and Sir Arthur C. Clarke in particular figured that there were three main types of spacecraft needed for the exploration of space: Space Ferry, Orbit-to-Orbit, and Airless Lander. Each is optimized for their own particular area of use.
More recently, orbital propellant depots and their related tanker ships also seem like a good piece of infrastructure. There are some sample realistic designs here, here, here, here and here. Not to mention here and here.
However, space warships are an entirely different kettle of fish.
The space ferry concept is what evolved into the NASA space shuttle. Its function is to boost payload into orbit, though you can think of it as an "atmospheric lander." Refer to the section on Surface To Orbit.
These are sometimes called "interface vehicles" because their function is to transport payload through the interface boundary between Terra's atmosphere and airless space.
The idea was to re-use as much of the rocket as possible, which is why the upper section has wings and the lower stages had parachutes. In Robert Heinlein's Space Cadet, the rocket is launched from a rocket sled going up the side of Pike's Peak. Nuclear powered rockets could boost more massive payloads, but a space elevator could boost so much more cheaply and efficiently.
Hop Davis estimates that space ferries launching from Terra will require a delta-V budget of around 10 kilometers per second (with orbital propellant depot) and require a thick atmosphere for aerobraking. It will require a bit more if there is no orbital depot, but not much more because coming down it uses aerobraking instead of propellant. The delta-V budget means they will probably have to be multi-stage if they are chemical rockets (good luck getting permission to use nuclear rockets). They will require a propulsion system with a thrust-to-weight ratio above 1.0.
Orbit-to-orbit spacecraft never land on any planet, moon, or asteroid.
Therefore they are free to use efficient propulsion systems with a thrust-to-weight ratio below 1.0, such as ion drives or VASIMR. They require no landing gear or parachutes. If there ain't no landing gear, it is an orbit-to-orbit. No streamlining is required either. They require no ablative heat shields unless they are designed to perform aerobraking to burn off delta-V without requiring propellant (like the Leonov in the movie 2010 The Year We Make Contact).
Hop Davis estimates that a orbit-to-orbit spacecraft will require a delta-V budget of only 3 to 4 kilometers per second, if orbital propellant depot are available. Otherwise it will be twice that, with along with a dramatic reduction in payload capacity. 4 km/s is well within the capabilities of a chemical rocket, but any higher and you will probably need staging or a propulsion system with more exhaust velocity.
The old image of orbit-to-orbit ships look like dumb-bells, the front ball is the cargo and habitat module, the rear is the propellant and radioactive atomic drive. The stick in between is a way to substitute distance for lead radiation shielding.
These are designed for landing on bodies that have no atmosphere, but you probably could get away with using them on Mars. They evolved into NASA's Apollo Lunar Module. So they will require some sort of landing gear. But no streamlining. They will require a propulsion system with a thrust-to-weight ratio near 1.0, depending on the surface gravity of the bodies they are designed to land on. This probably means chemical propulsion, maybe a solid-core NTR. Hop Davis estimates that airless lander spacecraft will require a delta-V budget of around 5 kilometers per second if orbital and surface propellant depots are available. Otherwise it will be twice that, with along with a dramatic reduction in payload capacity.
For sample designs, go to the Lander page.
So the smart way to design is to use an orbit-to-orbit spacecraft to travel between planets, and at a planetary destination use locally based surface-to-orbit services: either a space ferry, airless lander or surface-to-orbit installation at a spaceport.
But what if there are no locally available surface-to-orbit services? If NASA dispatches a Mars mission, there ain't no Martian space shuttles to ferry the crew down to the surface.
Making the entire spacecraft land-able is often a bad idea. For one, optimizing a spacecraft for both orbit-to-orbit and surface-to-orbit operations will probably result in an inefficient ship with the disadvantages of both and the advantages of neither. If you are designing with a weak propulsion system, it might not even be possible. And even if your propulsion system is up to the task, often it is better to park your ticket home in orbit where it is safe while other means are used to send crew into a possibly dangerous situation.
The standard solution is for the main spacecraft to carry small auxiliary spacecraft as landers, either aerodynamic space ferries or airless landers. The popular term from Star Trek is "Shuttlecraft".
A large space ferry shuttlescraft on modestly sized orbit-to-orbit spacecraft can make the ship look like an arrow.
Many aerospace engineers have pointed out that all of these spacecraft can be far more cheap and efficient if there were orbital depots of propellant and/or fuel established in various strategic locations where space travel is desired. This will necessitate some sort of tanker-type spacecraft to keep the depots supplied. They will be a species of orbit-to-orbit spacecraft optimized to carry huge amounts of propellant, and hopefully be unmanned drones or robot controlled. They can use an efficient propulsion system with thrust-to-weight ration below 1.0, ion or VASIMR. Like standard orbit-to-orbit, probably a delta-V budget of 4 km/sec, unless they are in a real hurry.
There will also be a species of airless lander optimized to carry propellant to planetary based depots, this is called a "lighter". As all landers the propulsion thrust to weight ratio will have to be near 1.0, probably chemical propulsion. As standard airless lander, probably a delta-V budget of 5 km/sec. The lighter will probably be designed to land a single modular tank from the cluster carried by the tanker.
(ed note: The Cargo ship section is quite long, click the Hide button if you want to skip over this section)
If spacecraft actually lands on a planet it may be a belly-lander instead of a tail-sitter, for ease of cargo loading/unloading. Otherwise it is like unloading cargo from the 25th floor window of a skyscraper.
Conventional cargo spacecraft have a conventional ship arrangement: a rocket engine aft of a cargo hold. You know, like pretty much every rocket you've ever seen: engines on the bottom.
The hold is an enclosed area to store cargo in, sections of which may or may not be pressurized. Unpressurized sections are for cheaper storage of inert durable cargo, e.g., raw ore. Pressurized sections are more expensive storage for delicate cargo that can be easily ruined by temperature and pressure extremes, e.g., produce and live animals.
The cargo hold may be rigged with attachment points for cargo containers. The hatches may be such to allow accessing individual containers. Alternatively the hold might be basically a huge tank. This is used for bulk cargo: liquids, gases, asteroid ore dust or gravel, grain, etc.
Cargo spacecraft might not bother with an enclosed area at all. Instead cargo containers are carried on the outside of spacecraft, attached to the ship's spine.
Unconventional cargo spacecraft have the rocket engine before the cargo hold. The engines are on the top.
This uses a waterskiing arrangement, with the engine and everything acting like a waterbound motorboat, dragging the cargo behind like a water skier. The rocket exhaust is angled such that it doesn't incinerate the cargo (but angled just barely enough to minimize thrust cosine loss). If the spacecraft carries relatively few cargo cans it is a Space Truck. If it carries long strings of cargo cans it is a Space Train. Yes, the boundary between a truck and a train is totally arbitrary.
Conventional cargo spacecraft may or may not be capable of landing on a planet (airless or with atmosphere). If the cargo ship cannot land and the local infrastructure is primitive, the cargo ship may have to carry landing shuttles to ferry cargo to and from the surface. If the local infrastructure is advanced, the ship can rent shuttle services from the local spaceport.
Unconventional cargo spacecraft are highly unlikely to be capable of landing at all. Certainly not if the planet has an atmosphere.
For transporting huge amounts of cargo, a safe bet is that the space industries will settle on a standard cargo container size. Because in the real world this lead to the miracle of Containerization. Which transformed global trade and built, nay even changed the world.
They would allow standardized design of cargo holds, they work well with space trucks and space trains, heck they work well as inert cargo vessels. Surface to Orbit services would probably be optimized to accommodate standard cargo container form factors.
Standarized cargo containers would become ubiquitous and cheap enough to find secondary markets for just the empty containers.
In the real world there are DIY people who alter shipping containers into inexpensive houses. In a RocketPunk future such containers can be tansformed into crude habitat modules by adding a few incidentals (plugging leaks, a bare bones life-support system, an airlock). Add some engines and you have a scratch-built spacecraft. Ikea in Space will probably offer inexpensive habitat modules based on shipping containers.
A new interstellar space colony on a shirt-sleeve habitable planet might bring along a commercial Farm From A Box to jump-start their agricultural self-sufficiency. Everything you need for a quick farm, neatly packed inside a shipping container. It's a kit!
Other "kits" mounted inside shipping containers include water treatment plants and electrical power generators. The military has shipping container kits containing medical surgery theaters, command and control facilities, and missile launchers.
And science fiction authors looking for an interesting (comments) background situation for their novel can pick up a few hints by doing a web search for news containing the search term "cargo container."
Eric Tolle was of the opinion that hexagonal cargo containers would probably be for bulk dry goods, Liquids would would best in cylinders or spheres, and containerized shipping would be best in rectangular cargo pods.
- Intermodal container
- Intermodal freight transport
- Twenty-foot equivalent unit
- Unit load
- Stowage plan for container ships
An intermodal container is a large standardized shipping container, designed and built for intermodal freight transport, meaning these containers can be used across different modes of transport – from ship to rail to truck – without unloading and reloading their cargo. Intermodal containers are primarily used to store and transport materials and products efficiently and securely in the global containerized intermodal freight transport system, but smaller numbers are in regional use as well. These containers are known under a number of names, such as simply container, cargo or freight container, ISO container, shipping, sea or ocean container, sea van or (Conex) box, sea can or c can.
Intermodal containers exist in many types and a number of standardized sizes, but ninety percent of the global container fleet are so-called "dry freight" or "general purpose" containers, durable closed steel boxes, mostly of either twenty or forty feet (6.1 or 12.2 m) standard length. The common heights are 8 feet 6 inches (2.6 m) and 9 feet 6 inches (2.9 m) – the latter are known as High Cube or Hi-Cube containers.
Just like cardboard boxes and pallets, these containers are a means to bundle cargo and goods into larger, unitized loads, that can be easily handled, moved, and stacked, and that will pack tightly in a ship or yard. Intermodal containers share a number of key construction features to withstand the stresses of intermodal shipping, to facilitate their handling and to allow stacking, as well as being identifiable through their individual, unique ISO 6346 reporting mark.
In 2012, there were about 20.5 million intermodal containers in the world of varying types to suit different cargoes. Containers have largely supplanted the traditional break bulk cargo – in 2010 containers accounted for 60% of the world's seaborne trade. The predominant alternative methods of transport carry bulk cargo – whether gaseous, liquid or solid – e.g. by bulk carrier or tank ship, tank car or truck. For air freight, the lighter weight IATA-defined unit load device is used.
Ninety percent of the global container fleet consists of "dry freight" or "general purpose" containers – both of standard and special sizes. And although lengths of containers vary from 8 to 56 feet (2.4 to 17.1 m), according to two 2012 container census reports about 80% of the world's containers are either twenty or forty foot standard length boxes of the dry freight design. These typical containers are rectangular, closed box models, with doors fitted at one end, and made of corrugated weathering steel (commonly known as CorTen) with a plywood floor. Although corrugating the sheet metal used for the sides and roof contributes significantly to the container's rigidity and stacking strength, just like in corrugated iron or in cardboard boxes, the corrugated sides cause aerodynamic drag, and up to 10% fuel economy loss in road or rail transport, compared to smooth-sided vans.
Standard containers are 8-foot (2.44 m) wide by 8 ft 6 in (2.59 m) high, although the taller "High Cube" or "hi-cube" units measuring 9 feet 6 inches (2.90 m) have become very common in recent years. By the end of 2013, high-cube 40 ft containers represented almost 50% of the world's maritime container fleet, according to Drewry's Container Census report.
About 90% of the world's containers are either nominal 20-foot (6.1 m) or 40-foot (12.2 m) long, although the United States and Canada also use longer units of 45 ft (13.7 m), 48 ft (14.6 m) and 53 ft (16.15 m). ISO containers have castings with openings for twistlock fasteners at each of the eight corners, to allow gripping the box from above, below, or the side, and they can be stacked up to ten units high. Regional intermodal containers, such as European and U.S. domestic units however, are mainly transported by road and rail, and can frequently only be stacked up to three laden units high. Although the two ends are quite rigid, containers flex somewhat during transport.
Container capacity is often expressed in twenty-foot equivalent units (TEU, or sometimes teu). A twenty-foot equivalent unit is a measure of containerized cargo capacity equal to one standard 20-foot (6.1 m) long container. This is an approximate measure, wherein the height of the box is not considered. For example, the 9 ft 6 in (2.9 m) tall high-cube, as well as 4-foot-3-inch half-height (1.3 m) 20-foot (6.1 m) containers are equally counted as one TEU. Similarly, extra long 45 ft (13.72 m) containers are commonly designated as two TEU, no different than standard 40 feet (12.19 m) long units. Two TEU are equivalent to one forty-foot equivalent unit (FEU).
In 2014 the global container fleet grew to a volume of 36.6 million TEU, based on Drewry Shipping Consultants' Container Census. Moreover, in 2014 for the first time in history 40-foot High cube containers accounted for the majority of boxes in service, measured in TEU.
Manufacturing prices for regular, dry freight containers are typically in the range of $1750—$2000 U.S. per CEU (container equivalent unit), and about 90% of the world's containers are made in China. The average age of the global container fleet was a little over 5 years from end 1994 to end 2009, meaning containers remain in shipping use for well over 10 years
Other than the standard, general purpose container, many variations exist for use with different cargoes. The most prominent of these are refrigerated containers (a.k.a. reefers) for perishable goods, that make up six percent of the world's shipping boxes. And tanks in a frame, for bulk liquids, account for another 0.75% of the global container fleet.
Although these variations are not of the standard type, they mostly are ISO standard containers – in fact the ISO 6346 standard classifies a broad spectrum of container types in great detail. Aside from different size options, the most important container types are:
- General-purpose dry vans, for boxes, cartons, cases, sacks, bales, pallets, drums, etc., Special interior layouts are known, such as:
- rolling-floor containers, for difficult-to-handle cargo
- garmentainers, for shipping garments on hangers (GOH)
- Ventilated containers. Essentially dry vans, but either passively or actively ventilated. For instance for organic products requiring ventilation
- Temperature controlled – either insulated, refrigerated, and/or heated containers, for perishable goods
- Tank containers, for liquids, gases, or powders. Frequently these are dangerous goods, and in the case of gases one shipping unit may contain multiple gas bottles
- Bulk containers (sometimes bulktainers), either closed models with roof-lids, or hard or soft open-top units for top loading, for instance for bulk minerals. Containerized coal carriers and "bin-liners" (containers designed for the efficient road and rail transportation of rubbish from cities to recycling and dump sites) are used in Europe.
- Open-top and open-side containers, for instance for easy loading of heavy machinery or oversize pallets. Crane systems can be used to load and unload crates without having to disassemble the container itself. Open sides are also used for ventilating hardy perishables like apples or potatoes.
- Platform based containers such as:
- flat-rack and bolster containers, for barrels, drums, crates, and any heavy or bulky out-of-gauge cargo, like machinery, semi-finished goods or processed timber. Empty flat-racks can either be stacked or shipped sideways in another ISO container
- collapsible containers, ranging from flushfolding flat-racks to fully closed ISO and CSC certified units with roof and walls when erected.
Containers for Offshore use have a few different features, like pad eyes, and must meet additional strength and design requirements, standards and certification, such as the DNV2.7-1 by Det Norske Veritas and the European standard EN12079: Offshore Containers and Associated Lifting Sets.
A multitude of equipment, such as generators, has been installed in containers of different types to simplify logistics – see containerized equipment for more details.
Swap body units usually have the same bottom corner fixtures as intermodal containers, and often have folding legs under their frame so that they can be moved between trucks without using a crane. However they frequently don't have the upper corner fittings of ISO containers, and are not stackable, nor can they be lifted and handled by the usual equipment like reach-stackers or straddle-carriers. They are generally more expensive to procure.
Basic dimensions and permissible gross weights of intermodal containers are largely determined by two ISO standards:
- ISO 668:2013 Series 1 freight containers—Classification, dimensions and ratings
- ISO 1496-1:2013 Series 1 freight containers—Specification and testing—Part 1: General cargo containers for general purposes
Weights and dimensions of the most common standardized types of containers are given below. Values vary slightly from manufacturer to manufacturer, but must stay within the tolerances dictated by the standards. Empty weight (tare weight) is not determined by the standards, but by the container's construction, and is therefore indicative, but necessary to calculate a net load figure, by subtracting it from the maximum permitted gross weight.
Container 20' 40' 40' high-cube 45' high-cube 48' 53' External
Length 19 ft 10.5 in
40 ft 0 in
40 ft 0 in
45 ft 0 in
48 ft 0 in
53 ft 0 in
Width 8 ft 0 in
8 ft 0 in
8 ft 0 in
8 ft 0 in
8 ft 6 in
8 ft 6 in
Height 8 ft 6 in
8 ft 6 in
9 ft 6 in
9 ft 6 in
9 ft 6 in
9 ft 6 in
Length 19 ft 3 in
39 ft 5 45⁄64 in
39 ft 4 in
44 ft 4 in
47 ft 6 in
52 ft 6 in
Width 7 ft 8 19⁄32 in
7 ft 8 19⁄32 in
7 ft 7 in
7 ft 8 19⁄32 in
8 ft 2 in
8 ft 2 in
Height 7 ft 9 57⁄64 in
7 ft 9 57⁄64 in
8 ft 9 in
8 ft 9 15⁄16 in
8 ft 11 in
8 ft 11 in
Width 7 ft 8 1⁄8 in
7 ft 8 1⁄8 in
7 ft 6 in
7 ft 8 1⁄8 in
8 ft 2 in
8 ft 2 in
Height 7 ft 5 3⁄4 in
7 ft 5 3⁄4 in
8 ft 5 in
8 ft 5 49⁄64 in
8 ft 10 in
8 ft 10 in
Internal volume 1,169 cu ft
2,385 cu ft
2,660 cu ft
3,040 cu ft
3,454 cu ft
3,830 cu ft
Empty weight 4,850 lb
Net load 61,289 lb
Each container is allocated a standardized ISO 6346 reporting mark (ownership code), four letters long ending in either U, J or Z, followed by six digits and a check digit. The ownership code for intermodal containers is issued by the Bureau International des Containers (International container bureau, abbr. B.I.C.) in France, hence the name BIC-Code for the intermodal container reporting mark. So far there exist only four-letter BIC-Codes ending in "U".
The placement and registration of BIC Codes is standardized by the commissions TC104 and TC122 in the JTC1 of the ISO which are dominated by shipping companies. Shipping containers are labelled with a series of identification codes that includes the manufacturer code, the ownership code, usage classification code, UN placard for hazardous goods and reference codes for additional transport control and security.
Following the extended usage of pallet-wide containers in Europe the EU started the Intermodal Loading Unit (ILU) initiative. This showed advantages for intermodal transport of containers and swap bodies. This led to the introduction of ILU-Codes defined by the standard EN 13044 which has the same format as the earlier BIC-Codes. The International Container Office BIC agreed to only issue ownership codes ending with U, J or Z. The new allocation office of the UIRR (International Union of Combined Road-Rail Transport Companies) agreed to only issue ownership reporting marks for swap bodies ending with A, B, C, D or K – companies having a BIC-Code ending with U can allocate an ILU-Code ending with K having the same preceding letters. Since July 2011 the new ILU codes can be registered, beginning with July 2014 all intermodal ISO containers and intermodal swap bodies must have an ownership code and by July 2019 all of them must bear a standard-conforming placard.
Containers come in many different types, each with a designation to distinguish the different types and uses. Designation for each container is (size)(type)/(tech level). There are three sizes of containers, coded as 4A (8 dtons or 112 cubic meters), 4C (4 dtons, 32 m3) or 4D (2 dtons, 16 m3). Containers are 3 meters high by 3 meters wide, and include all doors and fittings for cargo handling equipment. The size 4A containers are 12 meters long, 4C containers are 6 meters long, and 4D containers are 3 meters long.
Cargo Container Types
Container types Type Code Name Description 00 General Purpose A simple box with doors at both ends. 05 Sealed Same as type 00, but capable of being sealed against external atmosphere. Does not include life support or environmental controls. 32 Controlled Environment A type 05 but including environmental controls for heat and cooling. Can maintain any temperature between -35°C and 50°C. Requires external power supply, and has a 24 hour battery power supply. 50 Open Top Same as type 00, but missing the top. 55 Open Frame An open box frame with structural cross members. Used as a frame for heavy equipment. Can be covered with a flexible covering. 67 Modular A box designed to come apart into the six sides. Can be used as a type 00, type 50, or type 55, or folded flat for shipment. Four flat containers can be shipped in the space of one assembled container. 70 Tank A type 55 with a tank for transporting liquids or gasses in bulk. 90 Habitat A modular office, building component, or habitat. Provides full life support and cramped cabin quarters. Requires external power supply for life support, and has a 24 hour battery supply.
(ed note: This is a modification to the rules for the Traveller role playing game. But the reasoning is of general interest to cargo starship designers. Costs are in Traveller "credits" or CR, more or less equivalent to $1 US)April 2014 issue.
Why are standard cargo containers in Traveller 3m wide, 3m high and 6m long? Because no one consider the implications of containerized cargo on Earth when they wrote that description decades ago. Nor did they consider the standards for starships in Traveller. The standard cargo container, as written, is unusable in the standard starships, as written, in Classic Traveller.
A subsidized merchant (Type R) cannot stack two standard cargo containers in its hold because the deck height is only 6m. There would be no room to maneuver them about. From past experience working in steel yards and manufacturing plants, I would say as a minimum the decks would need to be 6.3m apart in order to safely stack two 3m containers, and it seems the writers of Fire, Fusion, & Steel 2 would agree because they suggest a minimum door size that is 10% larger in dimension than the corresponding dimension of anything that will be moved through it.
So let’s take a fresh look at containerized cargo for Traveller. On Earth, while there are occasionally containers dented by mishandling, it is rare, so a Traveller armor rating of 1 seems to be a reasonable ‘guesstimate’. This is also the standard minimum for grav vehicles, probably for much the same reason.
If the deck heights will be 3m then the maximum height of cargo containers should be 2.7m since starships will be the primary mode of transport. Does anyone know the Imperium’s standard axle size? Never mind, we’ll leave the other two dimensions at 3m and 6m. An Imperial standard shipping container would have a surface area of 84.6m2 and an external volume of 48.6 m3. Other important measurements depend on composition, per the table below.
Standard Cargo Container Measurements TL Material Volume* Mass (kg) Cost (Cr) 0 Light Wood 42.557 2.417 1,813 1 Wood 45.683 2.334 1,167 3 Iron 48.205 3.163 633 4 Soft Steel 48.252 2.785 558 5 Hard Steel 48.304 2.366 592 6 Titanium Alloy 48.403 1.578 1,973 7 Light Composite 48.452 1.037 1,038 8 Composite Laminate 48.501 0.790 790 9 Light Ceramic Composite 48.482 0.711 1,067 10 CrystalIron 48.526 0.742 668 12 Superdense 48.558 0.635 593 16 Collapsed CrystalIron 48.570 0.385 651
* Internal volume available to shipper, in m3
Containers are inexpensive and finding them “repurposed” to other functions would be quite likely. Researching “container architecture” might offer some ideas.
None of these would be vacuum resistant and the TL 0 and 1 containers couldn’t be made so. Adding a cargo door (e.g. one that was proof against vacuum) would add to the cost. Since most starships maintain shirt-sleeve environments in cargo areas this usually won’t be a problem; however, for high end cargos it might be worth a shipper’s while to pop for the added protection.
Cost of Vacuum-resistant Cargo Containers TL Cost (Cr) TL Cost (Cr) 3 3,647 8 6,825 4 4,708 9 6,582 5 4,604 10 7,131 6 5,661 12 7,540 7 6,227 16 7,707
A container could hold a kiloton of high density material so planetary standards bodies would probably call for a maximum gross mass. What that would be IYTU would depend on what standards exist for cargo moving equipment. Present-day ISO standards call for a maximum net load of 28.2 tonnes but present-day standard cargo containers are 21% smaller than those described here, so 38 tonnes would be comparable on a volume for volume basis.
There are probably sub-containers available as well. These would be designed to fit inside the main container with little wiggle room. They might be standardized or not IYTU. Because they are protected by the main container they would have no minimum standards and could be as simple as plastic or cardboard boxes. Standard widths would be 2.8, 1.4, 0.93, 0.7, 0.56, 0.46, 0.4, 0.35, and possibly 0.31, 0.28, 0.25, and 0.23. Standard lengths would be 5.8, 2.9, 1.93, 1.45, 1.16, 0.96, 0.82, 0.72, 0.64, 0.58, 0.52, and 0.48. Standard heights would be less likely, especially on the smaller end, but if you had them they would probably be on the order of 2.4, 1.2, 0.8, 0.6, 0.48, 0.4, 0.34, 0.3, 0.26, 0.24, 0.21, and 0.2.
Note that the widths and lengths refer to their placement within the main container. One could have sub-containers that were longer from side to side of the main container than they were front to back, relatively speaking.
Most PCs won’t know or care what’s inside the shipping containers in the hull, but if you have PCs that do something other than standard merchant type activities this information could be useful. There are actually companies that arrange sub cargos for small concerns that cannot afford to ship full containers and they make good money saving their customers money on shipping by bundling their shipments with others to form full containers.
I am arbitrarily defining a conventional cargo ship as one with the engines in the aft section of the spacecraft, while space trucks and space trains have the engines in the fore section (like an 18-wheeler or a choo-choo train). The only difference between space trucks and space trains is the number of cargo cannisters.
As attractive as is the admirable reduction in radiation shield mass offered by the waterskiiing spacecraft concept, there are practical problems in being towed on the end of a kilometer-long cable.
But the bit about using tension instead of compression members is still a worthwhile idea. Take some species of space tug, mount the propusion system on outriggers so the exhaust does not fire directly back along the ship's spine, and attach cargo modules to massive couplings on the bottom of the thrust frame.
As with all cargo spacecraft, delicate cargo will be housed in pressurized temperature-controlled cannisters but bulk ores and other insensitive cargo will just be dragged along in nets.
Space Truckers haul relatively small numbers of cargo modules, often attached to a framework. However if the tug is hauling a long chain of cargo modules, this is more like a freight train with a locomotive at the front and a string of freight cars in tow. A "space train" as it were.
Much like railroad locomotives, this will be less like loading crates into a seagoing container ship and more like latching cargo cans into long strings terminating at the rocket engine at the top.
This was the lead ship for the warp superconvoys, the 100-kilometer cargo carriers that revolutionized interstellar industrial transport. Configured in 8-ship linked octogons at the head of the convoy, with 4-ship squares of booster tugs after each 10-container segment, and all controls subspace-radio synchronized, these superconvoys transported billions of kilograms per superconvoy.
Specifications Length 225 m Beam 220 m Draught 45.6 m Mass 72.5 million kg Ship's Complement Officers
5 Crew 61 Std Ship's Complement 66 Performance Range 2000 light-years Cruising Speed Empty - Warp 3.5
Loaded - Warp 2
Engines Adv 3rd Gen Warp Drive Fuel 1:1 matter/antimatter Notes Tractor beam coupling for cargo containers
Most powerful thrust in starship history
SUPERCONVOYS OPEN NEW ERA OF TRADE: Billion ton ships are boon to industry (2161)USS MULETRAIN, PROVIDER CLASS
ALBERTO SABELLA, CHIEF ENGINEERING OFFICER
It's working! Warp effect is being engaged, and this superconvoy is rolling! Next stop—Centauri Spaceworks.
I'll let the boys upstairs take the glory, but the truth is old greasemonkey Sabella down here in the Engine Room is who straightened this whole mess out, I must admit in all humility.
Problem: how to transport raw materials from whistle-stop asteroid belts in the boondock sectors to the space factories of the UFP? And I'm not talking a freighter or two here. I'm talking about the billions and billions of metric tonnage needed each stardate to feed the Federation's ravening industrial plant. Star Fleet is stymied.
Solution: Sabella to the rescue. lt's elementary, I patiently explain, what we need are warp convoys of a hundred freighters and more. It can't be done, sneer the design baboons. No ship could produce a warp effect that great. Who said anything about one ship? I reply.
So I spelled it out for them. At the head of the convoy, assemble a configuration of heavy warp-drive tugs, say eight of them in an octagon. Lock their controls together and use the whole pile as the inertial driver. Next, string out a dozen or so of those new kilometer-long cargo cans, coupling them with tractor beams. Then—and here my brilliance staggers even my own modest self—plug in another configuration of warp tugs, four should do it, and knit the rest of the convoy with the same pattern, synchronize it all with subspace radio so that all warp engines engage simultaneously, and ride into the sky!
It can't be done, cry the designers.
An interesting conjecture, muses star Fleet.
It can be done, admit the designers in wonderment. Maybe only warp 2 or so, but this would save years of travel time, and trillions of credits.
Trillions? asks Star Fleet. Maybe we'll consider it. They considered it, they did it, it's done.
Merely brilliant, Sabella, I say. Merely brilliant.
LARGEST SPACELIFT EVACUATES DOOMED PLANET (2165)USS ENDURANCE, MANN CLASS
OKURU NELSON, ADMIRAL
Our flagship Endurance has run a final sensor scan of Bayard’s Planet, and I can report with certainty that not a single inhabitant has been missed by this, the largest spacelift in history. None too soon either. The shock wave from the supernova explosion that destroyed the Kepler will reach this systems sun in less than three star-dates, and it is 100 percent probable that it will initiate a chain reaction nova.
And the nova will destroy all life in the star system. All oceans will boil away; the gamma ray bombardment will scorch the surface; the planet itself may undergo an internal disruption and blow apart. it was imperative that Bayard’s Planet be evacuated. But how to evacuate ten million inhabitants? With the biggest spacelift ever.
Every starship within a fifty light-year radius was pressed into the effort by special request of the UFP. And I am just amazed by the response. Cruisers, destroyers, scout-ships, corvettes, all rendezvoused. Also trading clippers, low-warp tugs, even pleasure crafts of every type all rallied to the cause.
But all these valiant volunteers twice over could not have removed ten million people in time. Then an engineer in Star Fleet Merchant Marine named Sabella came up with the novel idea of refitting those new super-convoys with life support and jury-rigged decks. And that turned the corner for us. Starbase 5 renovated two superconvoys to accommodate passengers in an amazingly short time, and after weeks of impossible logistics and unmeetable timetables, we have succeeded in evacuating the entire planet. The galaxy has never seen an operation of this scope before. And I for one fervently hope it never has to again.
This is far more speculative, since as far as we know there have not been any space warships created yet. Refer to Warship Design, Warship Gallery, Space War: Intro, Space War: Detection, Warship Weapons Intro, , Warship Weapons Exotic, Space War: Defenses, Space War: Tactics, and Planetary Attack.
Fundamentally they are weapons platforms, so by definition they will be carrying various weapons systems. They may or may not have armor or other defenses, they may or may not have human crews. They probably will have an over sized delta-V capacity, and a large thrust capacity so they can jink around and complicate the enemy's targeting solution (i.e., dodge around so you are harder to hit). Lasers will require large amounts of power, and huge heat radiators and heat sinks to cope with waste energy. They will probably be carrying little or nothing that cannot be used to attack the enemy.
Space Arks are an outer-space version of that old Noah story: some cosmic apocalypse is going to obliterate the world, so it behoves the human race to evacuate to another world a breeding population of humans, a civilization starter kit, as much of the worlds scientific knowledge and culture they can cram in, and a viable subset of Terra's ecosystem (with redundancy, none of this "two by two" nonsense). Yes, it is a popular scifi trope.
It is basically a colony ship to establish an interstellar colony. Except the stakes are higher and the build time is limited. The time limit is set by the arrival date of the apocalypse. Designing it won't be easy. If the ship can be designed to be indefinitely habitable (a "worldship") then the journey to a safe place can be done leisurely. But since such ships are generally built in a clawing rush, they have a limited life until their warranty runs out. So the journey has to be as fast as possible.
Another challenge is attempting construction of the space ark while all the selfish people in the entire freaking world try to seize it for their own survival.
The space ark can be a generation ship or a sleeper ship. A popular option is putting an engine on the end of a space colony. A more challenging option is putting an engine on Terra large enough to move the entire planet somewhere safer. But that is out of the scope of "types of spaceships." Or is it?
John Brunner's epic novel THE CRUCIBLE OF TIME is about an alien race whose planet is faced with annihilation by an oncoming nebula. However the focus in the novel is more on the thousands of years before the building of the ark. The aliens are starting with medieval levels of scientific ignorance and do not even know they are in danger. It is a race to see if they can develop enough science to make space arks before the nebula clobbers them.
- The Epic of Gilgamesh
- Battle for Terra
- Titan A.E.
- Sky Captain and the World of Tomorrow
- After Earth
- The Bear with the Knot on His Tail by Stephen Tall
- Olias of Sunhillow by Jon Anderson
- Star Trek TOS "For the World is Hollow and I Have Touched the Sky"
- Warhammer 40,000's Eldar craftworlds
- Halo universe megastructure "The Ark"
- When Worlds Collide
- Born of the Sun by Jack Williamson
- Outpost video game
- Building Harlequin's Moon by Larry Niven and Brenda Cooper
They are lofted into orbit by either a chemical booster or laser launch service. Or manufactured in orbit; with Maw, Paw, and their brood buying tickets on a passenger service then taking possession.
At the cheapest they are basically a habitat module which rents propulsion services from a space tug, momentum bank, or a power-beaming service. Mid-range models will be something like a hydro ship, with some efficient and cheap (but low thrust) integral propulsion system. Top-of-the-line will be something approaching a full blown space tug, with enough delta-V to haul cargo.
These are examined in more detail here.
As mentioned in the section on Ice Mining, when it comes to the industrialization and colonization of space, water is the most valuable substance in the Universe. Among other things it can be used for life support, reaction mass, and radiation shielding.
There will be lots of robot asteroid miners, many who will specialize in volatiles such as water. These include the CFW NEO MicroMiner, the Robot Asteroid Prospector (RAP), the Asteroid Provided In-Situ Supplies (APIS), the Kuck Mosquito, the Water Truck, and the Water Ship.
There is a prototype life support system (and cosmic ray radiation shield) called the Water Wall that is mostly composed of water.
There is even a rocket engine called the Microwave Electrothermal Thruster which uses water for reaction mass, has a respectable exhaust velocity of up to 9,800 m/s, is very reliable, and can easily be powered by solar panels. Oh, and unlike ion drives, you can make massed clusters of the little darlings and they won't electromagnetically interfere with each other. You can make an array of 400 or so to produce a whopping 12,000 Newtons of thrust. They are also very easy to repair. Even by an amateur.
Best of all, if you mix water with a binder and freeze it, you get Pykrete, which is a building material. You could even use it to, well, build a spaceship or space station with. This turned up in Neal Stephenson's science fiction novel Seveneves, but there is no reason it couldn't be done in reality.
Which means you could make a spacecraft that was mostly water.
For an example, see the Spacecoach below.
Now this would not be suitable to make space battleships or space fighters with, but it would be dandy for interplanetary wagon trains for Maw and Paw Kettle to go homesteading in the asteroid belt. Mostly made of water, which cheaply comes from in-situ resource utilization. Not the strongest nor the most durable, but very affordable.
This would also be useful for somebody with limited access to raw materials. Say, refugees from a galactic war entering a remote uninhabited star system, carrying only whatever odd bits of material and tools that will fit into the cargo space not filled with refugees.
In 2010 Brian S. McConnell and Alex Tolley developed the Spacecoach concept and published it in a paper Reference Design for a Simple, Durable and Refuelable Interplanetary Spacecraft. This relatively low cost orbit-to-orbit spacecraft would be admirably suited for wagon trains in space. They could actually open up the solar system to pioneers if coupled with a low-cost surface-to-orbit transportation system such as a laser launcher. But McConnell and Tolley think the mass could be brought down enough to bring it within the boost capacity of, say a SpaceX Falcon 9 or Falcon 9 Heavy.
The basic premise of the spacecoach is to create a fully reusable orbit-to-orbit spacecraft that uses water and waste gases from crew consumables as its primary propellant.
So the design makes the consumables mass do double duty: first as life support for the crew, then as propellant. This drastically lowers the mass of the spacecraft, thus lowering the cost.
This also removes the incentive to install an expensive and cantankerous closed ecological life support system. Yes, supplies for a multiple year journey take up a lot of mass, but since it can be lumped under the heading of "propellant" it does not matter as much.
The water component of the consumables can do triple or quadruple duty. Before it is used as propellant, it can also serve as radiation shielding, supplemental debris shielding (as pykrete), and thermal regulation. In his simulation boardgame High Frontier developer Philip Eklund called water "the most valuable substance in the universe", and he was not kidding.
The spacecoach is also mostly constructed of water, in the form of pykrete. Very little metal is to be used. Actually it is very much like the composite ship from The Martian Way
The spacecoach will have sizable solar cell arrays used to power some species of electric rocket. There is some research underway to determine which of the many electric propulsion systems works best with water.
Ion drives, VASIMR, and helicon double layer rockets won't work because they are electricity hogs. They need to be fed by a nuclear reactor or equivalent, solar cells are too weak. Besides the insane price tag on a reactor and the ugly mass penalty, governments will be dubious about entrusting Maw and Paw Kettle with nuclear energy. They do have wonderful exhaust velocities, but the price is just too blasted high. Some won't even work with water as propellant.
Hall Effect Thrusters, Microwave Electrothermal Thruster (MET), and Electrodeless Lorentz Force Thruster (ELF) are much more suitable. They require much more modest amounts of electricity. Their exhaust velocities are weaker than the electricity hogs, but they are still much more potent than puny chemical rockets. These drives are also simpler to fabricate (i.e., cheaper, more reliable, lightweight, durable, and easily serviced). They can be clustered into arrays in order to increase the thrust. Electricity hog drives start interfering with each other if you cluster them.
The MET is especially simple. It isn't much more than a metal tube with a microwave magnetron attached. No moving parts either. It is sort of like a cross between a rocket engine and a microwave oven.
Current research shows a MET using water propellant can crank out a good 8,800 m/s exhaust velocity (Isp 900 sec) while an ELF can do about 16,700 m/s (Isp 1,700 sec). A Hall Effect thruster using water could theoretically do 29,000 m/s (3,000 sec) but researchers are still trying to figure out how to adapt them to water propellant.
For back-of-the-envelope calculations figure a spacecoach engine can do from 7,900 m/s to 20,000 m/s exhaust velocity (Isp 800 sec to 2000 sec). Compare this with chemical rocket's pathetic 4,400 m/s (450 sec).
20,000 m/s might not be quite enough to manage a trip to Ceres (10.593° inclination to ecliptic means a lot of delta V is needed), but the performance may be improved with more research.
The low thrust also minimizes the need for mass-expensive structural members.
McConnell and Tolley do have several design competitions open.
This is from Water Walls Life Support Architecture: 2012 NIAC Phase I Final Report (2012)
The idea here is to make a environmental control life support system (ECLSS) with a higher redundancy and reliability by making it passive, instead of active. Meaning instead of needing a blasted electrically-powered water-pump moving vital fluids around, use special membranes so that the vital fluids automatically seep in the proper direction. Fewer points of failure, fewer moving parts, no electricity needed, much more reliable.
The system harnesses the power of Forward Osmosis (FO), which mother nature has been using for the last 3.5 billion years since the first single-celled organism. Each unit has two compartments A and B, which share a wall made out of what they call a "semi-permeable membrane".
Compartment A contains contaminated water. Compartment B contains a solution (the "draw solution") which attracts water like a magnet using osmotic pressure. The contaminated water gets sucked through the semi-permeable membrane but leaves the contaminants behind (because the membrane won't let them through). The pure water (or purer water) winds up in compartment B with the draw solution and the contaminants remain in compartment A.
Since osmotic pressure is used there is no need for an electrical-powered water pump. It happens naturally just like a ball rolling downhill.
The research team noted that there already exists a commercial example of this: the X-Pack Water Filter System by Hydration Technology Innovations. You put nasty river water full of toxins and pathogens in compartment A and add a special sports-drink syrup into compartment B as draw solution. In about 12 hours compartment B will be filled with a refreshing sterile non-toxic sports-drink and all the horrible crap will be left behind in A.
So the research team realized that they could make a full ECLSS if they could develop some different types of forward osmosis bags and connect them together. They need bags that can do CO2 removal and O2 production (via algae), waste treatment for urine, waste treatment for wash water (graywater), waste treatment for solid wastes (blackwater), climate control, and contaminant control.
As a bonus cherry on top of the sundae, since all these will basically be bags of water, they can do double duty as habitat module radiation shielding.
The reliability comes from using lots of independent inexpensive disposable bags. The current system depends on driving an electromechanical water pump until it fails, then frantically trying to repair the blasted thing before all the toilets back up. Because the FO bags are cheap and low mass, they can be considered disposable, the spacecraft brings along crates of them with the other life support consumables. Because each bag uses forward osmosis as a built-in pump, there is no single point of failure. When one bag or cluster of bags, or integrated module of bags uses up their capacity, you switch the water line to the next units in sequence. The used bags can be cleaned, filled, and reused. Alternatively they can be stuffed somewhere in the habitat module to augment the radiation shielding.
|Specific Power||4.8 kW/kg|
|Thrust Power||484 megawatts|
|Specific Impulse||450 s|
|Exhaust Velocity||4,400 m/s|
|Wet Mass||350,000 kg|
|Dry Mass||100,000 kg|
|Mass Flow||49 kg/s|
|Initial Acceleration||0.06 g|
Kuck Mosquitoes were invented by David Kuck. They are robot mining/tanker vehicles designed to mine valuable water from icy dormant comets or D-type asteroids and deliver it to an orbital propellant depot.
They arrive at the target body and use thermal lances to anchor themselves. They drill through the rocky outer layer, inject steam to melt the ice, and suck out the water. The drill can cope with rocky layers of 20 meters or less of thickness.
When the 1,000 cubic meter collection bag is full, some of the water is electrolyzed into hydrogen and oxygen fuel for the rocket engine (in an ideal world the bag would only have to be 350 cubic meters, but the water is going to have lots of mud, cuttings, and other non-water debris).
The 5,600 m/s delta-V is enough to travel between the surface of Deimos and LEO in 270 days, either way. 250 metric tons of H2-O2 fuel, 100 metric tons of water payload, about 0.3 metric tons of drills and pumping equipment, and an unknown amount of mass for the chemical motor and power source (probably solar cells or an RTG).
100 metric tons of water in LEO is like money in the bank. Water is one of the most useful substance in space. And even though it is coming 227,000,000 kilometers from Deimo instead of 160 kilometers from Terra, it is a heck of a lot cheaper.
Naturally pressuring the interior of an asteroid with live steam runs the risk of catastrophic fracture or explosion, but that's why this is being done by a robot instead of by human beings.
In the first image, ignore the "40 tonne water bag" label. That image is from a wargame where 40 metric tons was the arbitrary modular tank size.
There are more details here.
|Specific Power||9.6 kW/kg|
|Propulsion||Solid core NTR|
|Specific Impulse||198 s|
|Exhaust Velocity||1,942 m/s|
|Wet Mass||123,000 kg|
|Dry Mass||30,400 kg|
|Total ΔV||2,740 m/s|
|Total Propellant||92,600 kg|
|Boost Propellant||75,700 kg|
|Landing Propellant||16,900 kg|
|Boost ΔV||1,859 m/s|
|Landing ΔV||881 m/s|
|Mass Flow||155 kg/s|
|Initial Acceleration||0.25 g|
|Tank Length||8.5 m|
|Total Length||11.9 m|
|Guidance Package||0.45 tons|
and Feed Lines
|Landing System||0.68 tons|
|25% Growth Factor||2.09 tons|
The Lunar ice water truck is a robot propellant tanker design by Anthony Zuppero. Its mission is to boost 20 metric tons of valuable water from lunar polar ice mines into a 100 km Low Lunar Orbit (LLO) cheaply and repeatably. It is estimated to be capable of delivering 3,840 metric tons of water into LLO per year.
This design uses a nuclear thermal rocket with currently available materials, and using water as propellant (a nuclear-heated steam rocket or NSR) instead of liquid hydrogen). This limits it to a specific impulse below 200 seconds which is pretty weak. However, numerous authors have shown that a NSR could deliver 10 and 100 times more payload per launched hardware than a H2-O2 chemical rocket or a NTR using liquid hydrogen. This is despite the fact that the chemical and NTR have much higher specific impulses. NSR work best when  the reactor can only be low energy,  there are abundant and cheap supplies of water propellant, and  mission delta-Vs are below 6,500 m/s.
The original article describes the water extraction subsystem at the lunar pole. It is a small reactor capable of melting 112.6 metric tons of ice into water (92.6 metric tons propellant + 20 metric tons payload) in about 45 hours. This will allow the water truck to make 192 launches per year, delivering a total of 3,840 metric tons of water per year.
Since the water truck is lifting off under the 0.17 g lunar gravity, its acceleration must be higher than that or it will just vibrate on the launch pad while steam-cleaning it. The design has a starting acceleration of 0.25 g (about 1.5 times lunar gravity).
The landing gear can fold so the water truck will fit in the Space Shuttle landing bay, but under ordinary use it is fixed. The guidance package mass includes radiation shielding. In addition, the guidance package is on the water truck's nose, to get as far as possible away from the reactor. The thrust structure and feed lines support the tank and anchor the reactor. The 25% growth factor is to accommodate future design changes without having to re-design the rest of the spacecraft. The reaction control nozzles perform thrust vector control. They take up more mass than a gimbaled engine, but by the same token they are not a maintenance nightmare and additional point of failure.
The reactor supplies about 120 kilowatts to the tank in order to prevent the water from freezing. The reactor mass is 50% more than minimum. The lift-off burn is about 20 minutes durationa and consumes 0.7 kg of Uranium 235.
|Specific Power||31 W/kg|
|Propulsion||Solid core NTR|
|Specific Impulse||190 s|
|Exhaust Velocity||1,860 m/s|
|Wet Mass||299,030,000 kg|
|Water tank mass||25,000 kg|
|Sans Payload Mass||148,000 kg|
|Payload mass||50,000,000 kg|
|Dry Mass||50,148,000 kg|
|ΔV|| 802 m/s|
 1280 m/s
 752 m/s
|Mass Flow||[1,2] 903 kg/s|
 2,684 kg/s
|Thrust||[1,2] 1,680 kiloNewtons|
[1,2] 4,990 kiloNewtons
|Nozzle Power||[1,2] 4.9 gigawatts|
 1.6 gigawatts
|Engine Power||[1,2] 12.1 gigawatts|
 4.1 gigawatts
|Initial Acceleration|| 0.0006 g|
 0.0009 g
 0.005 g
The Water Ship is a robot propellant tanker design by Anthony Zuppero. Its mission is to deliver 50,000 metric tons of valuable water from the Martian moon Deimos to orbital propellant depots in Low Earth Orbit (LEO) cheaply and repeatably. It is not much more than a huge water bladder perched on a NERVA rocket engine. It might have integral water mining equipment as does the Kuck Mosquito, or it might depend upon a seperate Deimos ice mine.
Mass of water bladder is 25 metric tons (rated for no more than 0.005 g). Mass of nuclear thermal rocket plus strutural mass is 123 metric tons (struture includes computers, navigation equipment, and everything else). Mass without payload is 25 + 123 = 148 metric tons. Payload is 50,000 metric tons of water. Dry mass is 148 + 50,000 = 50,148 metric tons. Propellant mass is 248,882 metric tons. Wet mass is 50,148 + 248,882 = 299,030 metric tons.
At Deimos, only about 4.55 megawatts will be needed to melt 299,000 metric tons of ice into water (50,000 tons for payload + 249,000 tons for propellant). The engine nuclear reactor can supply that with no problem. The water must be distilled, because mud or dissolved salts will do serious damage to the engine nuclear reactor. By "serious damage" I mean things like clogging the heat-exchanger channels to cause a reactor meltdown, or impure steam eroding the reactor element cladding resulting in live radioactive Uranium 235 spraying in the exhaust plume.
Nuclear thermal rocket was designed to be a very conservative 100 megawatts per ton of engine. Engine will have a peak power of 12,142 Megawatts (for stage  and ). This works out to a modest engine temperature of 800° Celsius, and a pathetic but reliable specific impulse of 190 seconds. A NERVA could probably handle 300 megawatts per ton of engine, but the designer wanted to err on the side of caution. This will require much more water propellant, but there is no lack of water at Deimos.
This design uses a nuclear thermal rocket using water as propellant (a nuclear-heated steam rocket or NSR) instead of liquid hydrogen). This limits it to a specific impulse below 200 seconds which is pretty weak. However, numerous authors have shown that a NSR could deliver 10 and 100 times more payload per launched hardware than a H2-O2 chemical rocket or a NTR using liquid hydrogen. This is despite the fact that the chemical and NTR have much higher specific impulses. NSR work best when  the reactor can only be low energy,  there are abundant and cheap supplies of water propellant, and  mission delta-Vs are below 6,500 m/s.
It is true that electrolyzing the water into hydrogen and oxygen then burning it in a chemical rocket will get you a much better specific impulse of 450 seconds. But then you need the energy to electrolyze the water, and equipment to handle cryogenic liquids. These are just more things to go wrong.
In the table, , , and  refer to different segments of the journey from Deimos to LEO.
-  Start at Deimos. 497 m/s burn into Highly Eccentric Mars Orbit (HEMO). At apoapsis, 305 m/s burn into Low Mars Orbit (LMO)
-  At LMO periapsis, 1,280 m/s burn using the Oberth Effect to inject the water ship into Mars-Earth Hohman transfer orbit
-  270 days later at LEO periapsis, 752 m/s burn using the Oberth Effect to capture the water ship into Highly HEEO
- [x] Water ship does several aerobrakes until it reaches an orbital propellant depot in LEO
Total thrust time is about 10 hours.
Water ship's propellant has 15,137 metric tons extra as a safety margin. When it arrives, hopefully some of this will be available. It will take 322 metric tons of propellant for the empty water ship to travel from HEEO to Deimos, or 1,992 metric tons to travel from LEO to Deimos. Plus 0.139 gigawatts of engine power and 10 hours of thrust time.
Traveling from Deimos to LEO will consume about 12.7 kg of Uranium 235. Given the fact that Hohmann launch windows from Mars to Earth only occur every two years, the fuel in the engine nuclear reactor will probably last the better part of a century before it has to be replaced. The engine will be obsolete long before then.
For more details, refer to the original article.
This is a variant using frozen hydrogen instead of H2O. The attraction is using the frozen hydrogen to do double-duty as structural members as well as propellant. This allows a welcome increase in the spacecraft mass-ratio that is something wonderful.
There are three types of spacecraft considered in this paper in which the primary concern is the engineering of hydrogen ice. The first is an unmanned fusion-powered probe, in which hydrogen ice acts as structural material, radiation shielding, and fuel source. The second is an approach to on-orbit refueling with propellant transfer via hydrogen ice, and subsequent slushification. The third is an array of self-contained hydrogen ice satellites with embedded cryogenic avionics and detonation wave propulsion. Each of these innovative concepts depends on the behavior of hydrogen ice; hence a thermal analysis of sublimation-cooled hydrogen ice spheres is provided.
1.0 Why Iceships?
Unmanned interstellar probes powered by nuclear fusion require a minimum deadweight ratio (fraction of non-payload mass remaining after all fuel is expended) and minimum molecular weight of exhaust material. An innovative way to achieve this is for the fuel and the structural components of a fusion probe to be one and the same.
Among contenders, beryllium (molecular weight 8) is rather difficult to vaporize, leaving the prime choices as either water ice (molecular weight 18) or lithium (molecular weight 6) stiffened by boron (molecular weight 11) or carbon (molecular weight 12) fibers, being vaporized, ionized, and expelled as reaction mass until no structural components remain besides the payload and now-useless engine.
In the last case, recent analysis by J. B. Stephens et. al. at NASA-JPL suggests that even hydrogen ice (molecular weight 2 ) can be stiffened by admixture of fibrous or particulate material far beyond its normal pliability — about the same as butter. Hydrogen ice can also be adequately protected against sublimation by very modest insulation. A one meter radius sphere of hydrogen ice, insulated by a centimeter of low-density hydrogen ice fluff and one centimeter of layered reflector, can last ten years in Earth orbit.
What are the structural limits of fiber-stiffened water ice, hydrogen ice, and lithium? Is it preferable to filter out the fibers, adding them to the deadweight, or to add engine weight to allow them to also be ionized and added to the exhaust? And, in the case of a water-ice fusion spacecraft, can we legitimately refer to this as the ultimate steamship?
2.0 Hydrogen Iceship: Detailed Examination
This section of the paper concentrates on the hydrogen ice spacecraft concept, and consists of an introduction, thermal analysis, experimental results, conclusions, and suggestions for future research.
Much of this analysis was contributed by James Salvail, of SETS, Inc., Honolulu.
Rather than having astronauts perform extravehicular activity to chip off chunks of hydrogen ice for fuel, we visualize a spacecraft made of a structural cluster of hydrogen ice spheres which can be robotically detached, one at a time as needed, and melted or slushified in a conventional fuel tank.
2.1 Hydrogen Iceship: Introduction
A hydrogen ice spaceship can be modelled as a cluster of concentric metal spheres each of which has hydrogen ice filling the spaces between its spherical surfaces. Most of the mass of the spacecraft is composed of these spheres, with the mass of the engine, avionics, payload, and so on comprising a much smaller fraction. The spheres are designed to provide some structural capability and to maintain fuel in solid form until needed (at which point they are liquefied for propellant usage).
Concentric spheres are connected to each other by at least two rods made of a material that has very low thermal conductivity, such as hard rubber. This is necessary so that the spheres above the instantaneous level of the subliming ice surface do not move relative to each other. The outer shells are made of a highly reflective material, such as aluminized (more easily ionized in propulsion: lithium-ized) mylar, thick enough to provide reasonable structural integrity. The inner spheres are made of the same materials, but much thinner (<<0.1 cm), as they are merely radiation shields.
The radiation shields and outer hulls must contain enough sufficiently sized holes or pores so that sublimed hydrogen molecules are quickly lost into space. The evacuated spaces between the slowly receding ice surface and the outer hulls thus have negligable gaseous heat conduction because the gas is very rarified. Gas flux is small enough (barring close flyby of the sun, nuclear explosions, or laser heating) that heat convection is also negligible. Under the listed abnormal operating conditions, gaseous conduction/convection would still be much smaller than radiative heat transfer. The effects of varying sphere radii, radiation shield number/spacing, outer hull albedo, and external environment are investigated to optimize the design for cost, size, and lifetime.
2.2 Hydrogen Iceship: Thermal Analysis
Thermal analysis consists of temperature calculations for outer hull, radiation shields, fixed radii from centers, and (crucially) at ice surfaces. Hull and shields are sufficiently thin and heat conductive as to be effectively isothermal through their thicknesses.
The energy balance at the outer hull consists of incoming solar radiation, emitted radiation from both sides, incoming radiation from the adjacent lower surface, and downward gaseous heat conduction. The two sides of the outer hull have, in general, different albedos and emissivities (if, for example, painted black externally for stealth). These effects are described by:
Where Em is the emissivity of the natural metallic surface, Eb is the emissivity of the outer surface (possibly black), unsubscripted E is the emissivity of the adjacent lower surface. If the lower adjacent surface is a radiation shield, then E=Em . If the lower adjacent surface is the ice surface, then E=Eh the emissivity of the ice. Am, is the albedo of the natural metallic surface. T is temperature, with subscripts i and j denoting depth and time. fb is a geometric factor accounting for the smaller area of the adjacent inner surface. Sb is the Stefan-Boltzmann constant. Sc is the solar constant at 1 AU (Astronomical Unit). Kg is the gaseous thermal conductivity of hydrogen. r is the radial coordinate (from the center of the ice sphere). R is the heliocentric distance in AUs. The factor 4 in the right hand solar insolation term reflects the assumption of rapid rotation. Constant values are given in section 2.3 . This equation, and a related one for the moving ice surface (with an energy balance including upward radiation from the ice surface, downward radiation from the adjacent metal surface, heat conduction into the ice, and the latent heat energy due to sublimation) are the basis for the results of section 2.3 .
where dr is the distance between adjacent surfaces. A similar factor which accounts for the larger area of an adjacent outer surface is given by:
The energy balance at inner surfaces above the level of the receding ice includes emitted radiation from both sides, incoming radiation from adjacent surfaces above and below, and downward heat conduction. This is described by the equation:
In our model, the space above the ice is gas so rarified that conduction is negligible. Solving for temperature (as a function time) in closed form gives:
At the ice surface, the energy balance includes upward radiation from the ice surface, downward radiation from the adjacent metal surface, heat conduction into the ice, and the latent heat energy due to ice sublimation. This is given by the equation :
where Kh is the thermal conductivity of hydrogen ice, Hs is the latent heat of hydrogen ice, Ah is the albedo of the ice, B is the vapor pressure constant, M is the molecular weight of hydrogen, and Ru is the universal gas constant. This equation is one of the boundary conditions for the ice domain. Again, the derivative of T with respect to r is actually a partial derivative.
For the interior of the hydrogen ice, the heat diffusion equation (in spherical coordinates) is:
where Dh is hydrogen ice density, C is hydrogen ice specific heat, and t is time. For the sake of our computer simulation, the derivatives of the two previous equations are approximated as finite difference equations:
where x is a parameter that takes into account the possibility of unequal distances between nodes (x=1 when nodes are equidistant).
If we define an additional parameter y as:
where dt is the discrete time step, we can solve for Ti,j:
Since the boundary condition at the center of the sphere is:
or, in finite difference form upon solving for Ti,j:
We now have four equations for Ti,j, which form a system of nonlinear algebraic equations which are solved iteratively in the simulations to provide a temperature profile through the hydrogen ice sphere.
The flux due to sublimation of the hydrogen ice is:
where Th is the temperature of the ice surface.
Finally, we derive the distance of the ice surface from the sphere's outer surface as follows. The mass loss during a time interval t* is:
where r is the radius of the residual ice sphere at the beginning of the time interval and h is the thickness of ice sublimed during the interval. we expand this to:
We can also express mass loss during the time interval t* as:
where ravg is the average value of r during t*, and can be approximated as:
Which is substituted into the later expression for mass loss to give:
Equating this with the first expression for mass loss, and rearranging terms, gives:
We can numerically solve the cubic for h. If the time interval is small enough (h<<r) then we can neglect the term containing h3 , allowing the explicit solution:
and therefore the instantaneous distance of the receding hydrogen ice surface from the outer surface of the sphere is:
where Hj-1 is the distance at the beginning of the time interval.
The results of the computer simulation, and the values of the constants used in the above equations, are given in Section 2.3, below.
2.3 Hydrogen Iceship: Computer Simulation Results
Computer simulation based on the preceding analysis calculated temperature at outer surface, radiation shields, surfaces and interior of the hydrogen ice. Ice surface temperature allowed derivation of hydrogen gas flux and radial position of the receding ice surface as a function of time, and thereby deriving hydrogen ice lifetime. Various runs determined the effects of radiation shields, outer albedo, and outer hull radius, in normal conditions and in a simulated nuclear blast. Kirchoff's law was assumed for metallic and ice surfaces. Parameter values are as listed below:
Property/Parameter Value A Vapor pressure constant 6.17 × 109 dynes/cm2 B Vapor pressure constant 149.44°K Am Albedo of metal 0.95 Ah Albedo of hydrogen ice 0.65 Em Emissivity of metal 0.05 Eh Emissivity of hydrogen ice 0.35 Ch Specific heat of hydrogen ice 2.7 × 107 erg/g-°K Dh Density of hydrogen ice 7.06 × 10-2g/cm3 Kh Thermal conductivity of ice 1 × 107 ergs/cm-s-°K Hs Latent heat of hydrogen ice 6.2 × 109 ergs/g Sc Solar constant at 1 AU 1.3928 × 106 ergs/cm2-s Ti Initial temperature of ice 5°K M Molecular weight of hydrogen 2.0 g/g-mole Sb Stephan-Boltzmann constant 5.6 × 10-5ergs/cm2-s-°K Ru Universal gas constant 8.315 × 107 ergs/mole-°K
First, a 1 meter radius sphere with 50 radiation shields spaced 2 centimeters apart and natural metallic surface was simulated. The ice remained nearly isothermal at the initial temperature of 5°K, with a negligible temperature gradient and a near-constant mass flux of 17.8 nanograms/cm2-sec. The outer hull remained at a temperature of 236°K at 1 AU from the sun. After a simulated 10 years, the sphere had shrunk to 21 cm in radius, and the total lifetime was approximately 12 years.
Reducing the radiation shields from 50 to 10 had no effect. Painting the outer surface black (albedo = 0 for stealth) gave a tripled mass flux of 53.8 nanograms/cm2-sec, a surface temperature of 5.2°K, and a reduced lifetime of 4.2 years.
At 0.1 AU from the sun a 50-shield 1 meter shiny sphere stays at 5.81°K with a mass flux of 1.06 micrograms/cm2-sec, and a lifetime of 75 days. With 10 shields, a 1 meter shiny sphere stays at 6.39°K, with a mass flux of 10.5 micrograms/cm2-sec, and a lifetime of 35 days. Hence radiation shields are important for larger thermal loads, such as would occur if the hydrogen iceship mission began with a gravity assist swingby close to the sun.
The thermal effects of nearby nuclear detonation were simulated as a temporary change in heliocentric distance from 1.0 AU to 0.01 AU (where the radiative equilibrium temperature for a black body is 2808°K) for 20 seconds. If the outer metallic coat doesn't melt at the maximum temperature attained (2361°K), then the hydrogen ice adjacent to the outer surface peaks at 8.73°K, with a gas flux of 4.7 milligrams/cm2-sec, decreasing after 10 minutes to 5.85°K (ten shields) or 5.79°K (fifty shields), at which time the ice has receded 2.5 cm.
All other things being equal, the lifetime of a hydrogen ice sphere was found to be directly proportional to the first power of the the initial radius. Thus, a 2 meter radius sphere has a 24 year lifetime at 1 AU, and 2 years at 0.1 AU. For deep space missions, loss becomes rather small for spheres several meters in radius.
2.4 Hydrogen Iceship: Summary of Concepts
The greatest advantage for a hydrogen ice spacecraft is obtained if the craft is an unmanned monolithic composite solid cryogen with embedded insulation and superconducting avionics. As disclosed by J. Stephens at JPL (who generated the original concepts in 1984 and 1985, while in communication with this author), the primary intellectual properties for patent purposes are:
- Ice embedded insulation
- Vapor cooled insulation
- Isomer conversion catalyst integral with insulation (activated carbon)
- IR photon reflective and vapor conductive insulation (variable mesh cloth multi-layer insulation)
- Vapor cast crystalline hydrogen ice using nuclear magnetic resonance heating of non-crystalline ice
- Self-forming filamentary insulation from dispersed particles in the ice that cohere due to ice cleaning
The attributes of the primary intellectual properties are:
- Unitized design; ice is the cryogen, structure, propellant, shielding, absorber, power source, window, and insulation support during launch
- Superconducting temperature cryostat (<5°K for Hydrogen)
- Self-insulating solid cryogen
- Long lifetime in earth orbit
- Low cost materials (<$10/lb)
- Low cost fabrication (casting process)
- Low launch cost (withstand high acceleration forces)
- Low cost operation (efficient superconducting solid-state system)
- Acoustically quiet (no moving parts) so good for very accurate optics or interferometry
- Thermally stable (large thermal capacity well insulated)
- High density ice vapor cast and used at same temperature to avoid shrink stresses in the insulation and other components embedded in the ice
The ancillary intellectual properties enabled by the primary concepts are:
- Vapor cooled refractory insulation
- Neutron absorbing cryogen (Hydrogen)
- Microwave absorbing ice/insulation
- Microwave reflecting ice/insulation
The advantages of the ancillary concepts are:
- Laser tough shielding
- Neutron tough shielding
- Neutral and charged particle beam tough shielding
- Radar stealth
- Superconducting phased array radar
Concepts enabled by Cryostat primary and secondary concepts are:
- Propulsion and electric power systems:
- Solar powered ion rocket and superconducting magnet power generator and storage system
- Magnetohydrodynamic detonation wave ion rocket and superconducting magnet power generator and storage system (detonate layers of solid oxygen alternated with solid hydrogen)
- Guidance and control:
- Superconducting computer
- Superconducting gyroscope
- Superconducting magnet attitude control
- Superconducting radio and antenna
- Launch forces resistant structure:
- fiber reinforced composite ice
- Remote sensing synersensory systems in phased arrays in Cryostats orbiting in formation:
- Synthetic aperture superconducting phased array radar
- Synthetic aperture superconducting phased SQUID array Magnetic Anomaly Detection
- Synthetic aperture superconducting phased SQUID array Gravimeter
- Synthetic aperture superconducting phased array Altimeter
- Blue-Green synthetic aperture superconducting phased array lidar
- Thermal IR telescope spectrometer
This astonishingly rich set of concepts of Jim Stephens is only moderately challenged by demands of the interplanetary or interstellar regime, as opposed to the near-Earth applications originally envisioned.
Individual hydrogen ice spheres can be orbited by small boosters, and later assembled into a large spacecraft. Solid hydrogen is inherently safer than liquid hydrogen. The spheres can have embedded avionics, providing distributed redundant capability for the spacecraft at superconducting temperatures. Once assembled, the low accelerations typical of an ion, fission, or fusion propulsion would not endanger the inherently low tensile strength of hydrogen ice as a structural material. The hydrogen ice spheres would be between the crew (or radiation-sensitive instrumentation) and the nuclear propulsion, providing neutron-absorbant shielding at no extra cost.
Space exploration applications include:
- Outer planet explorer
- 1000 AU mission (TAU)
- Subterranean radar mapping of planets
- Manned Mars Mission
- Propellant transfer and storage for Space Station refueling depot (see 3.4)
2.5 Solar Hydrogen Iceship
Hydrogen ice can be a propellant other than by the already-stated means of slushification and combustion with oxygen, detonation-wave combustion with oxygen ice, or by fusion.
Hydrogen ice can be the basis of a very efficient solar heated spacecraft. As researched at Rockwell, it was first realized that energy was saved in skipping liquefaction of hydrogen ice and oxygen ice. It is more efficient to burn the vapor subliming from hydrogen and oxygen ice (kept in separate tanks). Sublimation rates can be raised by heating with off-axis solar reflectors. Solar heating becomes more efficient if the hydrogen ice has embedded carbon black, to increase light absorption.
Even more efficient is a scheme to use solar heating to ionize hydrogen, and keep the ions trapped at the focus with a superconducting magnetic bottle. This process can be enhanced by doping the hydrogen with a thermal electron emitter such as LaB6.
Combining these various concepts, we are led to the following. Hydrogen ice propellant, laced with carbon black and lanthanum boride, is heated by solar reflectors. The sunlight passing through the partially reflecting surface is absorbed by solar photovoltaic cells. Carbon-blackened hydrogen is heated, and the embedded thermal electron emitter provides ionization. Hydrogen ions are trapped by a superconducting magnetic bottle. The solar cells generate current, which is used to power an ion accelerator. Hydrogen ions and electrons are thrust away by the ion engine, and the spacecraft moves forward by reaction. We note that stray hydrogen ions curving back to the spacecraft can do very little damage, whereas conventional metal ion engines (cesium or mercury) run the risk of plating and electrical short-circuit.
2.6 Hydrogen Iceship: Future Research
Future areas of systems analysis for the hydrogen iceship include:
- Comparisons of fiber-stiffened water ice, carbon dioxide, lithium, or other alternatives to hydrogen ice
- Experimental determination of strength, stiffness, etc. for hydrogen ice with various fiber compositions (boron, carbon)
- Structural design optimization for various types of propulsion systems
- Exploration of the concept of detonation wave propulsion/attitude control with alternating layers of hydrogen ice and oxygen ice
- Sensor capabilities of phased arrays of embedded cryogenic detectors in a fleet of coorbiting iceships
- Relativistic kinematics of multi-staged interstellar iceships
Yes, the line between general ship types and specialized ship types is a bit fuzzy. I did the best I could.
A tanker is a specialized cargo vessel. Cargo vessels Cargo holds and a remarkably large mass ratio. Common carriers use standardized cargo containers. Bulk Cargo ships carry cargo not packaged in cargo containers, such as food grains or unprocessed ore.
Sometimes they try their hand at being amateur trade pioneers, which is a dangerous task for the professionals and insanely dangerous for the amateurs. If they try, they will have rudimentary planetary exploration gear.
Overt smuggler ships are designed to look exactly like a run-of-the-mill merchant ship, but equipped with secret compartments for contraband that is elaborately sensor-hardened to hide from custom agent hand-held scanners. Overt smuggler ships openly land at the planetary spaceport and try to act innocent.
Covert smuggler ships try to sneak past the orbiting custom ships and secretly land at a hidden rendezvous. They rely upon a drastically reduced sensor signature, and the stealth provided from the bulk of the planet.
A warship's payload section can include anti-spacecraft weapons, orbital bombardment weapons (for revolt suppression type spacecraft as well), weapon mounts, weapon control stations, combat information center, armor, point defense, weapon heat radiators and heat sinks, and anything else that can be used to mission-kill enemy spacecraft.
I have an entire page devoted to the theory and practice of warship design.